An aluminum alloy has a light weight and a high strength so that an aluminum alloy is used for durable goods. Especially, an aluminum alloy is recently being for parts of a motor vehicle or for a case of an electronic device such as a mobile phone.
Two methods are generally used for manufacturing an aluminum alloy product. According to one method, an aluminum board is processed through a press-forming method to form a case, and the case is covered with an anodic oxidation coat. The case covered with the anodic oxidation coat can be used for a long time without damage, and can have a surface having a clear color. However, when the aluminum board is processed through the press-forming method to form the case, it is difficult to form a rib for reinforcement of the case, a space for parts disposed in the case, and a boss for screw combination. Furthermore, because some shapes cannot be obtained through the press-forming method, a design of the case is limited.
According to another method, a case of an electronic device may be formed from an aluminum alloy through a die-casting method. When the case is formed through the die-casting method, it is relatively easy to form a rib for reinforcement of the case, a space for parts disposed in the case, and a boss for screw combination. Thus, a design of the case can be determined more freely. However, an aluminum alloy for a die-casting method includes various metallic or non-metallic additives such as silicon or the like to improve flexibility. When the die-casting method is progressed, the additives migrate to near a surface. Thus, even if the case is coated with an anodic oxidation coat and colored, smut appears on a surface so that the case cannot have a clear color. Thus, a method of forming an additional coating layer on the die-casting-formed cover may be used. However, when the cover is used for a long time, the additional coating layer may be stripped.
Thus, there is a require developing a novel aluminum alloy for a die-casting method such that the aluminum alloy has a light weight and a high durability and can form a uniform anodic oxidation coat to provide a product having a clear color as well as to easily form a product having various shapes. Furthermore, there is a require developing a novel aluminum alloy not using an additive including a heavy metal harmful to human being,